janhq/jan · warning · Error

No active MLX session found for model: ${modelId}

Error message

No active MLX session found for model: ${modelId}

What it means

Thrown by unload() when findSessionByModel(modelId) returns nothing — there is no active MLX session for that id, so there is nothing to stop. The extension does not silently no-op; it errors so callers know the model wasn't loaded. Note findSessionByModel itself throws on plugin errors (a different path).

Source

Thrown at extensions/mlx-extension/src/index.ts:325

        modelId,
        modelPath,
        port,
        mlxConfig,
        envs,
        isEmbedding,
        Number(this.timeout)
      )
      return sInfo
    } catch (error) {
      logger.error(`Error loading MLX model: ${JSON.stringify(error)}`)
      throw error
    }
  }

  override async unload(modelId: string): Promise<UnloadResult> {
    const sInfo = await this.findSessionByModel(modelId)
    if (!sInfo) {
      throw new Error(`No active MLX session found for model: ${modelId}`)
    }

    try {
      const result = await unloadMlxModel(sInfo.pid)
      if (result.success) {
        logger.info(`Successfully unloaded MLX model with PID ${sInfo.pid}`)
      } else {
        logger.warn(`Failed to unload MLX model: ${result.error}`)
      }
      return result
    } catch (error) {
      logger.error('Error unloading MLX model:', error)
      return {
        success: false,
        error: `Failed to unload model: ${error}`,
      }
    }
  }

View on GitHub (pinned to fad3f12a14)

Solutions

1. Guard unload calls with findSessionByModel (or getLoadedModels) and skip if absent.
2. Treat 'not loaded' as a no-op success in cleanup paths rather than an error.
3. Verify the modelId string matches the id used at load() time.

Example fix

// before
await engine.unload(modelId)

// after
const sInfo = await engine.findSessionByModel(modelId).catch(() => null)
if (!sInfo) return { success: true } // nothing to unload
await engine.unload(modelId)

const sInfo = await engine.findSessionByModel(modelId).catch(() => null)
if (!sInfo) return { success: true } // not loaded; treat as no-op
await engine.unload(modelId)

try {
  await engine.unload(modelId)
} catch (e) {
  if (/No active MLX session/.test(String(e))) return { success: true }
  throw e
}

When it happens

Trigger: Calling engine.unload(modelId) when the model was never loaded, was already unloaded, or crashed and its session entry was already purged; calling unload with a modelId that differs in casing/format from the loaded one.

Common situations: Cleanup/shutdown code unconditionally unloading all models; a user clicks 'stop' on a model that already crashed and was auto-unloaded; retry logic that re-issues unload after a prior success.

Related errors

• Model already loaded!
• No active MLX session found for model: ${opts.model}
• No active session found for model: ${modelId}
• MLX model appears to have crashed! Please reload!
• MLX model has crashed! Please reload!

AI-assisted analysis of janhq/jan@fad3f12a14 (2026-08-12). Data as JSON: /api/errors/7232227f65ec0537. Report an issue: GitHub.